Idle-Stop not working ... cold weather or fault ?

[ColinB]

My car's idle-stop system system seems to have stopped working for no apparent reason. I was putting it down to the cold weather (the handbook mentions several temperature-related factors that would inhibit it). But then I found this thread over on the HRV forums (with contributions from people who post to this forum as well):
http://www.hrvforums.co.uk/viewtopic.php?f=11&t=289
My symptoms are exactly as described there, i.e. in circumstances where the idle-stop used to work I now get the circled-A-with-a-line-through-it, sometimes accompanied by the low-battery symbol, and the engine keeps running. That's even after a longish journey to warm the engine and cabin properly and charge the battery. Ambient temperature here today was between 5 & 7 degrees.

Doesn't stop me using the car, and some people might think that finding a way to turn it off permanently is useful, but it's niggling.

Anyone else seeing anything like this ? Or conversely please post to confirm if your idle-stop is working perfectly in current temperatures.

[Skyrider]

My stop start is working as it should. I have had a couple of "Not working, low battery" indications which I take as the car knows what is going on  and all is well. Car batteries have a tough time during winter, I charge mine most weekends during the winter with a 5amp CTEK smart charger and it is surprising how long it can take to fully charge. The cars user manual recommends charging the battery occasionally.

[andruec]

Yup, me too. It is still working but it's often displaying 'A/C' where previously it wouldn't. I do have my vents set to 'foot and screen' but they've been that way a while and it's only in the last month or so that SS has been blocked by my aircon. Just seems that the A/C (or some part of the ventilation) is working hard.

This morning when I got to Banbury (after a fifteen minute run at fairly steady 50mph) I stopped at the M40 lights and..'A/C'. But at the next set of lights (blasted pedestrians, how dare they  ) it cut the engine as it should. Ten minutes later at my office gates..'A/C'.

My fan is on higher for longer at the moment on startup but it has gone back down to it's normal two bars by the time I get to Banbury of a morning.

I've never had it show the low battery symbol though.

[andruec]

From looking more carefully this morning I think mind is refusing to idle stop if the fan is on three bars are higher. It seems that on cold mornings it eventually settles down to alternating between two and three bars.

[ColinB]

When I was first getting used to how the idle-stop thingy worked, I noticed that the "A/C" indication on the multi-display had nothing to do with A/C. I have the manual ventilation system so I control the vent position, fan speed, and A/C separately. I saw that the idle-stop worked when I had the A/C running, but not when I had the vent position set to screen only irrespective of whether the A/C was switched on or not. So my conclusion was that "A/C" on the multi-display was Honda's way of telling you that idle-stop won't work if the car thinks you're trying to defrost or demist the screen. Some similar sort of logic may be happening with Climate Control. But the list of reasons why it might not work is so complex that it's almost impossible to work out what might be happening in any specific circumstances.

Regarding my original Q, it looks like it's only me (thanks for the input) so I'll need to investigate further. I'll try some battery voltage checks and taking the car for a really long run to charge it fully.

[richardfrost]

I have the H-RV and experience all the same issues. To be honest, I have stopped obsessing on whether the Stop/Start system is broken or not. I know it works, I just don't know when it works and I am no longer bothered. I think the software that decides whether to stop the engine or not was written in by someone who does not drive on busy UK roads with our mix of weather and short/long journeys with batteries which may or may not be fully charged. There  are too many variables to second guess the system so I have given up trying.

[ColinS]

As far as I can tell mine is working within the design parameters of when the auto stop is not available, which as far as I can tell are:

•   The vehicle did not exceeded 3 KM/H (2 MPH) before coming to a stop.
•   Reverse gear has been selected.
•   Humidity in car is too high.
•   The steering wheel has been turned.
•   The engine temperature either too high or too low.
•   The climate control temperature is set to maximum hot (Hi) or minimum cold (Lo)
•   Mode is set to screen defrost/demist.
•   If the actual cabin temperature and the set temperature on the climate unit is too great the climate control unit not will permit auto stop function.
•   The Higher the fan speed is set to can also have an influence on Auto Stop function
•   Battery or charging error.
•   Incorrect battery fitted to the vehicle (non auto stop battery).

Correct me if I am wrong but I think one or more of these will account for the situations you all describe.

[ColinB]

As far as I can tell mine is working within the design parameters of when the auto stop is not available, which as far as I can tell are:

•   The vehicle did not exceeded 3 KM/H (2 MPH) before coming to a stop.
•   Reverse gear has been selected.
•   Humidity in car is too high.
•   The steering wheel has been turned.
•   The engine temperature either too high or too low.
•   The climate control temperature is set to maximum hot (Hi) or minimum cold (Lo)
•   Mode is set to screen defrost/demist.
•   If the actual cabin temperature and the set temperature on the climate unit is too great the climate control unit not will permit auto stop function.
•   The Higher the fan speed is set to can also have an influence on Auto Stop function
•   Battery or charging error.
•   Incorrect battery fitted to the vehicle (non auto stop battery).

Correct me if I am wrong but I think one or more of these will account for the situations you all describe.

That's as maybe, all I can say is that I am driving the car exactly the same as before and in situations where it used to work it doesn't. The obvious factor is the cold weather but if others are finding it works in current ambient temperatures then that's probably unlikely as a cause. So the worrying one on your list is the penultimate one which - if that's the cause - is something I'd want to do something about.
 

I have the H-RV and experience all the same issues. To be honest, I have stopped obsessing on whether the Stop/Start system is broken or not. I know it works, I just don't know when it works and I am no longer bothered. I think the software that decides whether to stop the engine or not was written in by someone who does not drive on busy UK roads with our mix of weather and short/long journeys with batteries which may or may not be fully charged. There  are too many variables to second guess the system so I have given up trying.

Richard, thanks for this, I noticed your contributions over in the HRV forum. I agree it's probably not worth worrying about in itself, I just want to ensure it's not a symptom of something more serious.

[ColinS]

So the worrying one on your list is the penultimate one which - if that's the cause - is something I'd want to do something about.

Unfortunately that does look likely Colin.  Hope the list was of some use.

[richardfrost]

Richard, thanks for this, I noticed your contributions over in the HRV forum. I agree it's probably not worth worrying about in itself, I just want to ensure it's not a symptom of something more serious.

I agree, but I have concluded that it isn't. I am a software engineer and I think some of the software in our H-RVs (and presumably Jazzes) is just too complicated. And ColinS' list above of all the things that could affect the Stop/Start makes that abundantly clear.

To be honest, most of the time the thing does engage, it's hardly worth it, as I am usually only stopped for a few seconds. When you want it to kick in is when you have pulled up at the lights at the start of a long sequence or when you are at roadworks or a motorway holdup, and you don't want to turn off the ignition as you would lose the radio, sat nav, heated seat setting, auto hold setting etc..

What I would like is something  more nuanced than an on/off button for Stop/Start. For example, if Stop/Start is on, I might want to override it for a few moments rather than turn it off completely. Or I might want to force an engine stop but not turn off at the ignition - i.e. a driver selected stop/start, to keep all my settings active.

I think I am just going to turn the thing off though as I am convinced that for my personal driving situation, it adds no value and saves no fuel.

P.S. ColinS, where did you get your list from? Is that publicly available? Is it somewhere in the Handbook?

[mikebore]

I think I am just going to turn the thing off though as I am convinced that for my personal driving situation, it adds no value and saves no fuel.

I agree, difficult to believe that it saves much fuel, but I can believe it might improve urban pollution in high traffic areas if lots of cars are doing it.

[ColinS]

P.S. ColinS, where did you get your list from? Is that publicly available? Is it somewhere in the Handbook?

I simplified an article from another website https://hondakarma.com/ but there is an extensive list on pages 406-407 of the manual which includes some other more obscure things such as altitude, being stopped on a steep incline and the driver's seat belt not being fastened.

I'm sure they were all put in there for good reason, either to save the battery or for safety, but I tend to agree with you that it is all a bit complicated and, as we know, complicated things are more prone to failure.  I also believe if some of them were not in there, then people would complain about that.

I like your idea of a manual idle stop button.

The one other item in the list that ColinB may consider is "The capacitor unit condition is not good" (Page 406).

[John Ratsey]

I have the theory that the system checks the battery health when the engine is started by looking at the voltage across the starter motor. It may then make assumptions about how much charge is being put in or it may just decide that the battery is too low to allow auto stop to be used on that journey. I developed this theory when I went on a 100 mile mainly motorway journey after the Jazz had been standing for a couple of weeks and auto stop didn't want to work after 80 miles of motorway on what was a nice day (so no competition for power from the alternator). Once the car had been stopped and restarted the auto stop was fine.

If this theory is correct and the voltage is measured away from the battery itself then any slightly poor connections which create a voltage drop will be interpreted as a lower voltage at the battery. Check the connections on the battery itself. However, there is also the underlying suspicion that Honda might have skimped on the alternator capacity which struggles to meet the needs of European winter driving, particularly for shortish trips. The Mk 3 also seems to have a higher rate of battery self discharge than its predecessors. Perhaps more electronics which don't turn off are slowly leaking power when the car is stopped. A built-in solar panel would help keep the battery healthy (except for the vehicles stored under a roof).

[andruec]

I think I am just going to turn the thing off though as I am convinced that for my personal driving situation, it adds no value and saves no fuel.

I agree, difficult to believe that it saves much fuel, but I can believe it might improve urban pollution in high traffic areas if lots of cars are doing it.

Various tests of various manufacturers of cars suggest it can save between 5% and 10%. The same tests suggest that the break-even point is around two seconds. Any less than that and the cost of restarting is greater than the fuel saved.

I'd suggest though that rather than turning the feature off maybe people could just learn to work with it. The strategies below don't just help you manage idle-stop - they also make you a more efficient and safer driver.

Better anticipation of traffic flow should allow you to choose whether to come to a stop or slow right down instead. In stop/start traffic there's nothing to be gained from hanging off the rear bumper of the car in front. Instead of accelerator/brake/accelerator/brake/... try and find a crawling speed and gap size that allows you to just bimble along at a few mph.

If you're approaching the end of a queue you might as well slow down early. Time it right and you might never have to stop. If driving through a serious of roundabouts don't do it at top speed. Slow down a bit to give traffic waiting to enter ahead of you time to dissipate. Do it right and you might get through the entire run without stopping. Doing this you'll save fuel and reduce brake wear.

If you have no choice but to stop and you think it likely it will be for less than two seconds then moderate the pressure on the break pedal you can use enough to hold the vehicle but not enough to activate idle-stop.

It's all about driver skill and knowing how to operate your vehicle. 

[mikebore]

Various tests of various manufacturers of cars suggest it can save between 5% and 10%.

That is a very big number, which is failing my BS test

Maybe the explanation is in the definition/calculation of "5-10%"...can you give any links to help understand.